Various types of faulted circuit indicators ("FCI's") are well known in the industry. These devices are typically used to sense and detect electrical faults in overhead conductors. Examples of different FCI's include clamp-on type faulted indicators that clamp directly on the overhead conductor and test point type fault indicators that are strategically placed at certain test points on the conductor.
Many FCI's include a binary display device for indicating the presence of a normal/reset or fault condition in the overhead conductor. The display devices of most FCI's are actuated by an electromagnetic field that causes an indicator flag to rotate either 90 or 180 degrees. Because each side of the flag is colored or marked differently, the color or mark displayed on the indicator changes when the flag rotates or flips. A change in the color or mark of the indicator flag signals that a fault condition exists. Such indicators can be either manually reset after the fault condition disappears or electrically reset upon restoration of current in the overhead conductor. U.S. Pat. Nos. 3,460,038, 3,995,243, 4,157,520, 4,466,042, 4,495,489, 4,661,813, 4,694,599 and 5,159,319 provide a representative overview of some faulted circuit indicators of this type.
U.S. Pat. No. 4,495,489 teaches a FCI for indicating the occurrence of a fault in a power distribution system with a rotatably mounted indicator flag. The indicator flag is actuated through successive 90 degree trip and reset positions by an electromagnetic device and is visible through a pair of viewing windows located on the face of the FCI's housing. Similarly, U.S. Pat. No. 4,694,599 discloses an electromagnetic indicator capable of indicating a normal/reset or fault condition. The display device disclosed in that invention is a rotatably mounted semicircular flag assembly which rotates between trip and reset positions.
The displays of the FCI's presently on the market, such as those described above, are extremely difficult to view, particularly when mounted on overhead electric utility conductors. The indicators or display devices of these FCI's are usually configured in the traditional, two-dimensional flag-type shape. Under ideal conditions, therefore, the old FCI's require utility linemen to position themselves directly below the display device in order to ascertain the status of the display. Under less favorable conditions, the linemen must sometimes use binoculars to view the display device. This visibility problem hinders the ability of linemen to readily view the indicator of the display device to ascertain the status of the conductor and can often result in erroneous readings.
In an attempt to alleviate the above problem, some FCI manufacturers have added a battery and a flashing L.E.D. to increase the visibility of the display device. This approach, however, has proved inadequate for various reasons (e.g. batteries have been unacceptable to many utilities). Other attempts to enhance visibility through improved display designs have been equally unsuccessful.